Tube bending machine and mandril assembly



Oct. 3, 1967 F. SASSAK j 3,344,639

TUBE BENDING MACHINE AND MANDRIL ASSEMBLY Filed Dec. 15, 1964 3 Sheets-Sheet 1 INVENTOR FRANK SASSAK (da M ATTORNEYS Oct} 1957 F. SASSAK TUBE BENDING MACHINE AND MANDRIL ASSEMBLY 15, 1964 5 Sheets-Sheet 2 Filed Dec.

FRANK SASSAK MOI ATTORNEYS Oct. 3, 1967 F. SASSAK 3,344,639

TUBE BENDING MACHINE AND MANDRIL ASSEMB LY ATTORNEYS United States Patent 3,344,639 TUBE BENDING MACHINE AND MANDRIL ASSEMBLY Frank Sassak, Dearboru, Mich. (1033 Vermont Ave., Detroit, Mich. 48216) Filed Dec. 15, 1964, Ser. No. 418,399 1 Claim. (Cl. 72-150) ABSTRACT OF THE DISCLOSURE A tube bending machine is provided with an upper diemounted linkage for automatically withdrawing a mandril at a controlled rate from the tube as it is bent to permit the mandril to maintain position adjacent the shifting point of tangency between the tube and the upper die as the tube Wraps around the die.

The present invention relates to tube bending machines of the type disclosed in my co-pending patent application, Ser. No. 350,355, filed Mar. 9, 1964, now US. Patent No. 3,306,093, issued Feb. 28, 1967.

Heretofore, in the bending of tubes and pipes various mechanisms have been employed to prevent buckling of the tube and for maintaining a constant internal and exterior diameter. Devices of this type have been ineffective, cumbersome or too costly.

It is an object of the present invention to provide an improved tube bending machine together with a mandril assembly projected down into the tube ends to prevent buckling during bending and with means for effecting out- Ward movement of the mandril during bending so that the inner end portion of each mandril is always outwardly of and tangent to the curved portion of the tube being bent.

It is an object of the invention to provide in a tube bending machine a novel mandril assembly together with means for controlling the location of the mandril during bending,

These and other objects will be seen from the following specification and claim in conjunction with the appended drawings in which:

FIG. 1 is a front perspective view of a portion of the present tube bending machine with the die blocks in normal inoperative tube support position before the bending operation.

FIG. 2 is a front elevational view thereof with the associated forming die on the movable platen of a press.

FIG. 3 is a fragmentary plan view thereof.

FIG. 4 is similar to FIG. 2, but with the movable die moved downwardly in the tube bending operation.

FIG. 5 is a section taken on line 5-5 of FIG. 4.

It will be understood that the above drawings illustrate merely a preferred embodiment of the invention, and that other embodiments are contemplated within the scope of the claims hereafter set forth.

Referring to the drawings, FIGS. 1 and 3, a pair of spaced aligned support housings 12 and 13 form a part of the tube bending machine 11, and are adjustably secured upon the bed 14 of a press.

Housings 12 and 13 include at their inner ends the upright spaced supports 17. Shafts 15 at their ends are journaled within bearings 16 nested and retained within their respective upright supports 17, all as fully set forth in detail in co-pending application No. 350,355.

Mounted upon each of the shafts 15 and between the supports 17 are the pinions 18, FIGS. 1 and 2. Each pinion is in mesh with a longitudinally reciprocal rack gear 19 slidably mounted upon the interior of housings 12 and 13. Said gears at their inner ends are connected to a piston 20 movably sealed within a cylinder bore upon the interior of housings 12 and 13.

Housings 12 .and 13 include cylinder heads 21 at their outer ends with suitable passages which communicate with the interior of said cylinder bores outwardly of the respective piston therein. The closed conduits 22 join the respective cylinder heads 21 and also join each other by the flexible tubing 23, FIG. 1, which is provided since housings 12 and 13 are longitudinally adjustable with respect to each other upon support platen 14 and fixedly secured thereon, such as shown in copending application No. 350,355.

A source of air under pressure is delivered through pipe 24 through regulator 25 and pressure gauge 26, which communicates with tubes 22 for providing an initial constant air pressure upon the interior of cylinder housings 12 outwardly of pistons 20 normally resisting outward movement of said pistons and providing a reactive pressure during bending.

Spaced aligned horizontally disposed rotatable die blocks 27 are journaled upon the exterior of housings 12 and 13 adjacent supports 17 being fixedly secured as at 28 to shafts 15. Said die blocks are longitudinally grooved at 29 to support a tube T to be bent, FIG. 2. The radius of said groovesis substantially the same as the outside radius of tube T to provide support for said tube prior to and during the bending operation.

In the normal bending operation there is provided a pair of interconnected vertically reciprocal longitudinally spaced forming dies 32-34. These are vertically aligned with die blocks 27 and are mountable upon vertically reciprocal platen 31 which forms a part of a conventional press. The die assembly includes supports 30, FIG. 2, to which are secured the pairs of movable die elements 32, 34.

A die of this type is provided wherein the tube to be bent will have a central straight portion and outwardly thereof the respective ends of the tube will be bent upwardly at a pre-deter-mined angle. For this purpose the movable die elements include the spaced opposed aligned horizontally extending die portions 32 which terminate at their outer ends in the circular die portions 34.

Die elements 32 have longitudinal grooves 33 in their undersurfaces adapted to cooperatively register with the straight portion of tube T, 33. Said grooves correspond to the outside radius of said tube. The circular die elements 34 also have corresponding grooves 35 which merge with groove 33, being of the same radius, for cooperative engagement with the tube during the bending operation, FIG. 4.

The center distance 4545 between the circular die elements 34 is less than the center distance 28-28 between the rotatable die blocks 27, FIG. 1.

In the normal operation of the tube bending machine as the movable dies 3234 move downwardly from the retracted dotted line position, FIG. 2, to the solid line position and thence to the position shown in FIG. 4, the respective die blocks 27 will rotate to the angular position shown. This causes rotation of pinions 18 respectively on supports 17. This also causes retraction of the rack gears 19 and connected pistons Within the support cylinder housings 12 and 13. These retracting movements are resisted by the compressed air upon the interior of said housings, as fully set forth in co-pending application No. 350,355.

In the present tube bending machine there are incorporated a pair of straight mandril rods 42 which adjacent their outer ends have sleeves 41 of increased diameter and terminate in handles 44 of still greater diameter. The individual mandril rods 42 are adapted to be snugly and slidably projected into opposite ends of tube T prior to the bending operation, FIG. 2; and sleeves 41 operatively engage end portions of the tube limiting inward movement of the mandrils.

For a particular bending operation the inner ends 43, FIG. 2, of the respective mandrils are in substantial vertical registry with thecenter of curvature of the circular dies 34 corresponding to the beginning of that portion of the tube which is to achieve a curvature during the bending operation.

The principle of operation is that as the tube end portions are bent upwardly towards the positions shown in FIG. 4, central portions of the tube T adjacent the straight portion shown in FIG. 2 and FIG. 4 will be curved upwardly corresponding to the radius of the circular dies 3435. This means that as the tube curves around the circular dies, the straight mandril 42 must be retracted so as to remain at all times tangent to the circular forming dies 3435, and to thus prevent buckling of the tube during bending.

For this purpose there are provided a pair of linkages. Each linkage includes a pair of parallel spaced elongated links 3637, FIGS. 2 and 3 which have secured therebetween at their outer ends the control block 39. Said control block has a vertical slot 40 to cooperatively receive sleeve 41, FIGS. 2 and 5. The slot 40, however, is of a width less than the diameter of handle 44 so that block 39 is adapted to operatively engage the handle for efiecting outward movement of the mandril rods as required and during the forming operation. The respective spaced inner ends of links 36-37 are pivotally mounted at 45 to the center of curvature of the vertically movable dies 34.

Accordingly, upon downward movement of platen 31 and die assembly 32-34 there will be an upward bending movement of the free ends of tube T such as to the position shown in FIG. 4.

Thus, as the central inner portions of the tube are being bent the respective blocks 39 are effective to operatively engage the respective mandril handles 44 for retracting the same so that the inner end portion 43, in FIG. 2, within the tube has now become retracted as at 43', FIG. 4, so as to remain within the straight portion of the tube T.

This position is at all times tangent to the forming die 34 and to the curved portion of the tube as it is formed. As the tube bends, its straight portion is shortened. Block 39 through links 3637 stays at a constant distance from center 45.

Thus, during the downward forming movement of dies 32-34 and the upward formation of the tube ends, mandrils 42 are automatically retracted.

The length of linkage 3637 remains constant. Thus,

upward bending movement of the tube ends pivots the linkages 36-37 upward and causes a retracting movement of the mandril rods 42 continuously during the process of bending.

Having described my invention, reference should now be had to the following claim.

I claim:

In a tube bending machine characterized by an upper vertically reciprocable arcuate die and a straight lower die block rotatably and adjustably secured to the bed of the machine, beneath the upper die on an axis of retation offset from the path of the center of curvature of the upper die, the improved means for preventing crosssectional distortion in the bend zone of a tube being bent which comprises:

a mandrel having an inner end adapted to be inserted into a tube to be bent and an outer end;

a mandrel-positioning link pivotally mounted at one end to the upper arcuate die at the center of curvature thereof, the opposite end of said link being removably secured to said outer end of said mandrel;

the point at which said link is secured to said mandrel being so positioned along the length of said mandrel that, when said mandrel is inserted in a tube lying on the lower die block, said mandrel inner end lies substantially at the point of tangency of the tube and the upper arcuate die;

whereby when the upper arcuate die is driven downwardly into engagement with the tube, causing the lower die to pivot and the tube to bend, the swinging of the free end of the tube and said mandrel causes said link also to pivot, the pivoting of said link effecting a controlled withdrawal of said mandrel from the zone of the bend, such that said mandrel inner end remains at said tangency point as said tangency point shifts during the bending of the tube.

References Cited UNITED STATES PATENTS 2,440,599 4/ 1948 Colwell 72389 3,021,886 2/1962 Ferris 72389 3,112,787 12/1963 Dard 72150 3,155,139 11/1964 Hautau 72150 3,156,827 11/1964 Munro 72150 3,181,323 5/1965 Bos 72386 3,196,661 7/1965 Lance 72389 3,217,524 11/1965 Stanley 72-150 RICHARD J. HERBST, Primary Examiner.

E. M. COMBS, Assistant Examiner. 

